V. Jacobson. IP headers for low-speed serial links. RFC 1144, Internet Engineering Task Force, February 1990.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....that avoid link layer error detection. In this paper, we analyze the influence of these problems on existing header compression algorithms. We also propose an adaptive header compression that gives better performance. 1 Previous Work Van Jacobson proposed a TCP IP header compression algorithm [5] for low speed links. TCP IP packets with compressed headers normally traverse a single link, with a compressor on one side and a decompressor on the other. The idea is to avoid transferring redundant information whenever possible. The decompressor should use information already known to recover ....

V. Jacobson. IP headers for low-speed serial links. RFC 1144, Internet Engineering Task Force, February 1990.

....errored datagrams which were consecutive in TCP sequence number space. In these cases, the datagram length is incorrect and both the checksum eld contents and the TCP payload of a bad packet match the next good packet. One possible cause is decompression of a link using Van Jacobson [4] header compression (VJ HC) where the decompresser dropped a packet (perhaps due to a link level CRC error) When the receiver decompresses the next correctlyreceived packet of that ow after the drop, the decompresser will reconstitute the packet header from deltas which do not include the ....

....a packet (perhaps due to a link level CRC error) When the receiver decompresses the next correctlyreceived packet of that ow after the drop, the decompresser will reconstitute the packet header from deltas which do not include the sequence number delta of the dropped packet. see section 4. 1 in [4]) The net e ect is that sequence numbers are cut o each packet and pasted on to the succeeding packet. This continues until an end to end TCP retransmissions kick in, whereupon the backward jump in sequencenumber space causes the VJ HC sender to send an uncompressed header, which nally ....

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Jacobson, V. Compressing TCP/IP headers for low-speed serial links. Internet RFC 1144, Information Sciencies Institute, Feb 1990.

....specific functions, such as paging and simple message passing, carried by people walking around. Even with general purpose machines, people are unlikely to perform complicated work that requires a lot of network connections on the fly. 3 Related Work 3. 1 TCP IP Header Compression Van Jacobson [13] proposed TCP IP header compression for lowspeed serial links, and Degermark et al. 8] provides both UDP IP and TCP IP header compression mechanisms over wireless networks. Their basic observation is that among a stream of consecutive packets, a large part of the header does not change very ....

....addresses and port numbers of the source and the destination. The size of the new header would be 12 bytes for IPv4, in comparison with 28 bytes of the UDP IP header and 40 bytes of the TCP IP header. We propose to further reduce the METP header size by employing the idea of header compression in [13] and [8] We add 4 bytes to the full METP header to include a connection ID,asequence number and a few flags. When a TCP connection is established, a full METP header is used and both the mobile host and the base station record a binding of the connection ID and the address information of this ....

V. Jacobson. Compressing TCP/IP Headers for Low-Speed Serial Links. Network Working Group, Request for Comments 1144, February 1990.

....example, frame delivery delay on IS 95 is around 100ms. Reducing the datagram size again reduces FER at the expense of increasing header overhead. However, TCP overhead can be reduced to 3 5 bytes per datagram by employing header compression, a technique appropriate for low bandwidth serial links [15]. This optimization is feasible only for the TCP IP combination. Since CT systems use separate uplink and downlink channels, forward (data) and reverse (acknowledgment) traffic do not interfere as in the WLAN case. Rather surprisingly then, TCP offers potentially more bandwidth to the user than ....

V. Jacobson. Compressing TCP/IP headers for low-speed serial links. Internet Request For Comments, February 1990. RFC 1144.

....to specify which of the packet header s first 20 bytes have changed. Thinwire was relatively protocol neutral, but not optimized for common traffic. In early 1990, Van Jacobson proposed a TCP IP specific compression algorithm with many optimizations taking advantage of this protocol s intricacies [17]. Sending between 3 5 bytes of the 40byte header in the common case, VJ TCP header compression is efficient, and the most widely deployed header compression protocol. However, VJ compression only works with TCP IP packets, and derives many of its strengths from its rigid specification. Since ....

JACOBSON, V. Compressing TCP/IP Headers for Low-Speed Serial Links. Internet Engineering Task Force, Feb. 1990. RFC-1144.

....recent packet in the cache, for simplicity and performance. We strip packet headers including UDP TCP before searching for redundancy. This is not required for our analysis, but improves eciency, because headers are typically not repetitive. E ective schemes exist for compressing TCP headers [10]. As part of computing the number of redundant bytes, we charge each match region a small penalty that is intended to represent the space needed to encode it for transmission. We felt this penalty important because, if it were not present, we could ultimately detect 100 redundancy by observing ....

V. Jacobson. Compressing TCP/IP headers for low-speed serial links, February 1990. RFC 1144.

....related problems that affect transport layer performance in a mobile environment. We also describe some of the desirable features that a transport protocol specially developed for mobile hosts should have. 4.6. 1 Comparison with existing schemes Thinwire protocols [29] and TCP header compression [45] can help in improving the response time of interactive applications such as telnet on low speed links. However, these solutions do not deal with host mobility. Link layer retransmission (LLR) can be used on error prone wireless links to bring their error rate on par with that on the wired ....

....on behalf of the personal computer. TCP header compression was also suggested in the same proposal to reduce bandwidth requirements for single character transmission over the serial line. A more effective method for compressing TCP headers for low speed serial links was suggested by Van Jacobson [45] in 1990. As with thinwire protocols, this method also does not address the problems of lossy links and host mobility. A dynamic round trip time estimation scheme for the Rx RPC package used in AFS [34] was described in [6] to improve Rx performance over low speed SLIP links. 150 The proposed ....

V. Jacobson. Compressing TCP/IP headers for low-speed serial links. Request for Comments 1144, February 1990.

....end systems (i.e. a part of the installed software on all user computers) modifications are undesirable and difficult to manage. Therefore, alternative solutions to reduce ACK Congestion are needed to suit the characteristics of a DVB Network. 4. 1 TCP Header Compression TCP header compression [16] is widely used on modem links and may compress the TCP IP header. An ACK packet may be reduced by 70 over the return link. However, this compression ratio may not be sufficient to prevent ACK congestion when the asymmetric ratio is higher than 80. 4.2 ACK Suppression Another way to avoid ACK ....

....indicating potential data loss and triggering unnecessary retransmission of data. The TCP congestion control algorithms also trigger, reducing the transmission rate, and therefore throughput. Since ACKs arrive at the sender more quickly using header compression, the cwnd may grow more rapidly [16] (figure 3) However, 28 the compression ratio is not enough to eliminate ACK Congestion for a DVB network, which results in expiry of the TCP retransmission timer, and subsequent slow start. This results in only a small improvement in TCP throughput (figure 4) Unmodified (A) Number of ....

V. Jacobson, 'Compressing TCP/IP Headers for Low-Speed Serial Links', IETF, RFC1144,Feb 1990.

....can change significantly on short time scales over some network paths. A possible area of future work is to assess the stationarity of RTTs in the network (much as has been done for routes, loss rate and throughput [ZPS00] We now turn our attention to the second goal of this section. RFC 1144 [Jac90] suggests 100 200 ms as the amount of time that users can perceive in regards to responses from networks. We note that figure 9 shows that nearly 75 of the connections in the P 0 dataset experience average RTT delays over 100 ms and nearly 40 of the RTTs observed exceed 200 ms. This ....

Van Jacobson. Compressing TCP/IP Headers For Low-Speed Serial Links, February 1990. RFC 1144.

....version control represent intermediate versions as deltas; SCCS starts with an original version and encodes subsequent ones with forward deltas, whereas RCS encodes previous versions as reverse deltas from their successors. Jacobson s technique for compressing IP and TCP headers over slow links [11] uses a clever, highly specialized form of delta encoding. In spite of this history, it appears to have taken several years before anyone thought of applying delta encoding to HTTP, perhaps because the development of HTTP caching has been somewhat haphazard. The first published suggestion for ....

Van Jacobson. Compressing TCP/IP Headers for Low-Speed Serial Links. RFC 1144, Network Working Group, February, 1990.

.... detailed discussions of DCE and ASN.1, can be found in [BN84, Tan88, CS93, CDK94] On RPC performance, the classic reference is [SB89] Critiques of the RPC paradigm appear in [TR88, BR94] On the problem of inconsistent failure detection with RPC: BG95] Other relevant publications include [BCLF94, BCLF95, BD95, BKT90, BM90, BN84, Bro94, EBBV95, EKO95, GA91, HP94, Jac88, Jac90, MRTR90, Ras86, SB89, TL93]. A good reference to DCE is [DCE94] and to OLE 2 is [Bro94] Kerberos is discussed in [SNS88, BM90, Sch94] Kenneth P. Birman Building Secure and Reliable Network Applications 96 96 5. Streams In Section 1.2 we introduced the idea of a reliable communications channel, or stream, that could ....

....of recent work on optimizing streams protocols (particularly TCP) for high performance network hardware. An analysis of TCP costs, somewhat along the lines of the RPC cost Chapter 5: Streams 103 103 analysis in [SB89] can be found in [CJRS89] Work on performance optimization of TCP includes [Jac88, Jac90, Kay94, KP93]. A summary of other relevant papers can be found in [Com91, Ten90, BD95] Other papers included in the biliography of this text include [BMP94, Com91, CS93, CT87, DP93, EBBV95, FJML95, Jac88, Jac90, KC93, KP94, MRTR90, PHMA89, RAAB88a, RAAB88b, RST88, RST89, SDW92, Tan88, CDK94] Kenneth P. ....

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Van Jacobson. Compressing TCP/IP Headers for Low-Speed Serial Links. RFC 114, Network Working Group, February 1990.

....can change significantly on short time scales over some network paths. A possible area of future work is to assess the stationarity of RTTs in the network (much as has been done for routes, loss rate and throughput [ZPS00] We now turn our attention to the second goal of this section. RFC 1144 [Jac90] suggests 100 200 ms as the amount of time that users can perceive in regards to responses from networks. We note that figure 9 shows that nearly 75 of the connections in the P 0 dataset experience RTT delays over 100 ms and nearly 40 of the RTTs observed exceed 200 ms. This indicates that ....

Van Jacobson. Compressing TCP/IP Headers For Low-Speed Serial Links, February 1990. RFC 1144.

....by Internet hosts result in suboptimal performance due to the large delay bandwidth product of the DBS network. Because the connectivity of the earth station to the Internet is limited by a 1. 5 Mbps T1 line, the bandwidth asymmetry is adequately overcome by techniques such as SLIP compression [13]. However, the long latency and the limited reverse channel bandwidth increase latency for Web like accesses; we show that techniques such as persistent connections and pipelined requests (e.g. 24] lead to significant performance improvements. The rest of this paper is organized as ....

....(ack clocking [12] With asymmetric bandwidth, the flow of acknowledgements over the slow reverse channel could throttle the flow of data packets. One way of alleviating this problem is to reduce the size of the acknowledgement packets using techniques such as SLIP header compression [13]. Another is to send TCP acknowledgements less frequently (e.g. 16] although care must be taken to ensure that the sender does not become very bursty as a result. This may be achieved by regulating the transmission of data at a consistent rate within the TCP congestion window, using the ratio ....

V. Jacobson. Compressing TCP/IP Headers for Low-Speed Serial Links, February 1990. RFC 1144.

....recovery between TCP and RLP. In fact, we did not find any incidents of competing error recovery during bulk data transfers, as discussed in Section 6.4. All measurements that yielded a utilization of 95 percent or less suffered from the impact of RLP link resets when TCP IP header compression [12] was used. This is further explained in Section 6.3. Figure 6 also shows the throughput range that sock (see Section 4.1) achieved for measurements that yielded the same utilization. Taking protocol overhead into account, the throughput was consistently close to the bit rate of the channel. These ....

....both ends of wide area wireless links, which we believe will be the bottleneck in a future Internet. 6.3 The Impact of RLP Link Resets One of the key findings of our measurements and analysis is an understanding of the impact of RLP link resets (see Section 3.1. 1) when TCP IP header compression [12] is used to reduce the per segment overhead. As with other differential encoding schemes, header compression relies on the fact that the encoded deltas are not lost or reordered on the link between compressor and decompressor. Lost deltas will lead to false headers being generated at the ....

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Jacobson V., Compressing TCP/IP Headers for Low-Speed Serial Links, RFC 1144, February 1990.

....acknowledgements flowing in a direction opposite to data packets) causes the sender s round trip time estimate to be highly variable. This inflates TCP s retransmission timeout value, thereby impairing loss recovery. The following are our major results and conclusions: SLIP header compression [13] alleviates some of the performance problems due to bandwidth asymmetry, but does not completely eliminate all problems, especially those that arise in the presence of bidirectional traffic. Connections traversing packet radio networks suffer from large variations in round trip time caused by ....

....queue of packets and remove all redundant acks for the connection, taking care not to remove any acks that have data associated with them. A connection is uniquely identified by the 4 tuple port . In practice, packets on the PPP queue are often header compressed using the algorithm described in [13], which makes it hard to offset into the header and obtain the necessary fields. There are several alternative approaches to solving this problem: 1. Decompress the compressed packets in the queue each time a new ack arrives and compare fields. This requires maintaining extensive decompression ....

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V. Jacobson. Compressing TCP/IP Headers for LowSpeed Serial Links, February 1990. RFC 1144.

....as suggested in section 5 below) gab beefed up this section. Must add M TCP. 4.11 Header Compression Alternatives Because Long Thin Networks are bandwidth constrained, every byte that can be compressed out of over the air segments is worth compressing. Van Jacobson header compression [RFC1144] describes a Proposed Standard for TCP Header compression that is widely deployed. Mechanisms for TCP and IP header compression defined in [IPHC, IPHC PPP] provide the following benefits: Improve interactive response time Allow using small packets for bulk data with good line efficiency Allow ....

Jacobson, V., Compressing TCP/IP Headers for Low-Speed Serial Links, RFC 1144, February 1990.

....past. 2. It may be expensive to multiplex several data streams within a TCP session at a very fine granularity because of the overhead of the TCP IP header (usually 40 bytes or more) If this is really an issue, header compression techniques similar to those used for low speed dialup lines [52] could be used to reduce the overhead. 3. TCP session does not share any information across hosts. There are situation where this may be advantageous. For instance, two hosts on a LAN could benefit by sharing information about the network path to a common server. The SPAND system [97] points ....

....a slower rate than if there had been no queuing of acks. Another consequence is that the growth of the sender s window size slows down. This is part of the reason why the downstream throughput with a dialup upstream link running SLIP [95] is so low (Figure 9. 1) SLIP header compression (C SLIP) [52] reduces the sizes of acks and hence decreases k, thereby improving performance. For instance, consider bandwidths of 10 Mbps and 28.8 Kbps in the two directions, and a data packet size of 1 KB. With the TCP timestamp option enabled, the ack size is 52 bytes with SLIP and 18 bytes with C SLIP. So ....

V. Jacobson. Compressing TCP/IP Headers for Low-speed Serial Links. RFC-1144, Feb 1990.

....of the total link usage. Of course, there exist many slow speed links for instance voice band modems, and increasingly, wireless links. On these links, header size is an important issue. In fact, even the IP header, at 20 bytes, is too big for dial up links, and requires header compression [60]. Thus, we have situations where the largest (CLNP) of the three headers is no problem, and others where the smallest (small SIPP) is too big. Fortunately, there are mechanisms for reducing the negative impact of a large or deep header. Both of them have already been mentioned. If the problem is ....

V. Jacobson. Compressing TCP/IP Headers for Low-Speed Serial Links. Request For Comments 1144, University of Southern California Information Sciences Institute, February 1990.

....129 TCP IP ACK Figure 8: Example Station Identification Packet The conversation continues on as per the usual TCP IP method. 9 Transporting Compressed IP Over DUAL PR CIP In the design of DUAL, we believed it was possible to use the TCP IP header compression scheme used in Compressed SLIP [Jacobson 90] This would reduce header overhead from 18 40 octets (AX.25, IP, TCP) to 5 5 bytes (DUAL, compressed TCP IP) We wished to use the header compression scheme in such a way that the compressed headers did not grow in size, and any alterations to the scheme were small. This has been accomplished. ....

....down. This section will give an overview about how we are going to implement DUAL, and will discuss some of the basic idea and problem behind the compression algorithm. This implementation will use and modifies an existing SLIP CSLIP implementation. For more information about SLIP and CSLIP see, Jacobson 90] and [Romkey 88] respectively. 13 11.1 Implementation Overview As shown in Figure 13b) the implementation will modify the existing SLIP CSLIP implementation, Serial Lines IP, which is commonly used for point to point serial connections running TCP IP. The modification is mainly around the ....

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V. Jacobson. Compressing TCP/IP headers for low-speed serial links, RFC 1144, February 1990.

....However, the workstations are also used as clients of other workstations. All of the machines were idle during the tests. The network options consisted of switched 10 Mbit s Ethernet, 2 Mbit s wireless AT T WaveLAN, and Serial Line IP with Van Jacobson TCP IP header compression (CSLIP) [57] over 19.2 Kbit s V.32terbo wired and 9.6 Kbit s ETC cellular dial up links 1 . To minimize the effects of network traffic on the experiments, the switched Ethernet hub was configured such that the server, the ThinkPad Ethernet adapter, and the WaveLAN base station were the only machines on the ....

V. Jacobson, Compressing TCP/IP Headers for Low-Speed Serial Links, Internet RFC 1144, Feb. 1990.

....header encoding, compresses TCP IP headers through differential encoding. It takes advantage of the predictable changes between successive headers for the same TCP connection. Such an encoding scheme has been previously demonstrated to achieve a 10 to 1 compression ratio of TCP IP headers [15]. In our calculations, we assume the same compression ratio for 40 byte TCP IP headers but leave 28 byte UDP IP headers intact. Efficiency (percentage) Compression Technique 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 none Pad Stripping Cell Header Suppression Datagram Header ....

....is currently used in the Internet by hosts connected to low speed serial lines. Predictive differential encoding of TCP IP headers has been implemented with minor modifications to the Berkeley Software Distribution (BSD) Unix kernel. The nature of these modifications are documented in Reference [15]. They are also included in a Serial Line IP (SLIP) software distribution that has been used for several years throughout the Internet. The same techniques are applicable within an ATM network if each TCP connection maps to a separate virtual circuit in a connection oriented ATM network. However, ....

V. Jacobson, Compressing TCP/IP Headers for Low-Speed Serial Links, Network Working Group Request for Comments 1144, February, 1990.

....workstation based gateways) so that our modification has minimal impact on them. For example, IP Secure datagrams should have no trouble getting through Internet gateways. The IP Secure does not modify upper layer headers, so even mechanisms which does peak through such as TCP header compression [9] will continue to work. At the time of this writing, an initial implementation of IP Secure is complete for the PC AT compatible machines running BSD 386, and we are working on the SunOS 4.1.3 with NET 2 network module. Simple performance evaluation using two Gateway2000 (i486DX2 at 66MHz) showed ....

Van Jacobson. Compressing TCP/IP Headers for Low-Speed Serial Links. RFC 1144, February 1990.

....we will show that there is replicated traffic, e.g. gzip may search approximately 32KB, while we have detected significant correlation at 1000 times that scale. Another type of compression that is frequently employed is packet header compression. Schemes specialized for compressing TCP IP headers [7, 4] may reduce their impact by an order of magnitude in the best cases, and hence may have a significant impact on bandwidth usage when there are many short packets. In the packet traces we observed, however, the volume of headers was small compared with the volume of payloads, i.e. even eliminating ....

V. Jacobson. Compressing TCP/IP Headers for Low-Speed Serial Links. Request For Comments: 1144, February 1990.

....that need to be considered. At the same time, these parameters can vary suddenly and drastically. Existing support is not sufficient for adapting to these new parameters. Many variations of TCP have been proposed to deal with specific networks. TCP for space communication [16] TCP over SLIP [14] are some examples. However, having a new TCP for every possible network does not help when network conditions change dynamically. We need the ability to automatically change Application Layer Netif Network Transport Layer Table Lookup (per socket entries) Reporting to applications Protocol ....

V. Jacobson. Compressing TCP/IP headers for low speed serial links, 1990. Requests for Comments 1144.

....160 bits long, has about 126 bits of probable plaintext, and the TCP header has about 124 bits predictable out of 160. That there is considerable redundancy here is not surprising. Indeed, the same observation was made, albeit in a rather different context, in the design of PPP header compression [Jac90]. When predictable header fields are added to the redundancy in the user s data, it becomes apparent that exhaustive search cryptanalysis is quite feasible even without known plaintext. 6 Traffic Analysis Probable plaintext attacks are not carried out on a whim. They require expensive, ....

....defender s advantage. A more promising approach might be to use a keyed compression function. For example, the compression dictionary could be modified based on the keying material. A different approach to compression might be to use semantic knowledge, along the lines of PPP header compression [Jac90]. For example, it may be possible to send abbreviated sequence and acknowledgment fields. If per connection keying is used, IP addresses and port numbers are implicit in the security association and need not be sent. The replay counter is more troublesome; more or less by definition, it can t be ....

V. Jacobson. Compressing TCP/IP headers for low-speed serial links. Request for Comments (Proposed Standard) RFC 1144, Internet Engineering Task Force, February 1990.

....path trees, depending on receiver requirements. arrives, or when the MH leaves the area; then all MH state is deleted. Essentially, the proposed join and leave IGMP messages specify the difference between the existing and the new state of the MH. This is a variation on header compression [15], customized for IGMP. While with standard IGMP one query and multiple responses per time interval (as many as the groups a MH belongs to) are needed, with the new approach only one message per join and leave operation is required, regardless of the duration of group membership. This approach not ....

V. Jacobson. Compressing TCP/IP headers for low-speed serial links. Internet Request For Comments, February 1990. RFC 1144.

....Latencies are in milliseconds, throughput is in Mbit s. The network options consist of switched 10 Mbit s Ethernet, 2 Mbit s wireless AT T WaveLAN, 128 Kbit s and 64 Kbit s Integrated Digital Services Network (ISDN) links, and Serial Line IP with Van Jacobson TCP IP header compression (CSLIP) [14] over 19.2 Kbit s V.32terbo wired and 9.6 Kbit s Enhanced Throughput Cellular (ETC) cellular dial up links 2 . The test environment consisted of a single server and multiple clients. The server machine was a Intel Advanced EV workstation running the standalone TCP server. The clients were IBM ....

V. Jacobson. Compressing TCP/IP Headers for Low-Speed Serial Links. Internet RFC 1144, February 1990.

....section we will describe those parts of IPv6 header compression that are relevant for understanding the lookup problem. For a detailed description of IPv6 header compression, please refer to [2] 2.1. Functional Description Header compression was first described and implemented by Van Jacobson [5], who observed that IP traffic can be grouped into packet streams or flows. Within such a flow most of the header fields of consecutive packets are identical or change in a very predictable manner. With this in mind he designed a header compression scheme, which basically works as follows: The ....

....and is likely to slow down the lookup. The original IPv4 header compression scheme was targeted for IPv4 TCP over dial up links running at speeds of up to 9600 kbit per second. Bandwidth limitation guaranteed that there would only be a small number of flows simultaneously active. Van Jacobson [5] reported never seeing any thrashing using 16 CIDs. With such a small table the algorithm used in the lookup have very little impact on overall performance. However, for IPv6 header compression, which deals with larger and more complicated headers and is a likely candidate for links in the megabit ....

Van Jacobson, Compressing TCP/IP headers for low-speed serial links, Request for Comments (Proposed Standard) RFC 1144 , Internet Engineering Task Force, Feb 1990.

....This inflates TCP s retransmission timeout value, thereby impairing loss recovery. To appear, Proc. 3rd ACM IEEE Intl. Conference on Mobile Computing and Networking (MobiCom) Budapest, Hungary, Sept. 1997. 2 The following are our major results and conclusions: SLIP header compression [11] alleviates some of the performance problems due to bandwidth asymmetry, but does not completely eliminate all problems, especially those that arise in the presence of bidirectional traffic. Connections traversing packet radio networks suffer from large variations in round trip time caused by ....

....for acknowledgments and data requests, on end to end performance in the forward direction. We distinguished between bandwidth asymmetry, latency and media access asymmetry, and loss asymmetry, and focused on the first two types. The following are our main results: SLIP header compression [11] alleviates some of the problems due to bandwidth asymmetry, but does not completely eliminate all problems, especially those that arise in the presence of bidirectional traffic. Connections traversing packet radio networks suffer from large variations in round trip times caused by the ....

V. Jacobson. Compressing TCP/IP Headers for Lowspeed Serial Links. RFC-1144, Feb 1990.

....telnet and NFS traffic. These results show delays in the wireless network ranging from 0.2 seconds to several hundred seconds. Note that even the minimum latency is noticeable to users, since previous reports show that users begin to find interactive response time slow when it exceeds 100 to 200ms [12]. The median delays are painful, but not hopeless: the telnet median is 0.97 seconds and the NFS median is 0.6 seconds. Sixty percent of telnet delays are 1.3 seconds or less, and sixty percent of NFS delays are 0.7 seconds or less. However, the high end of the scale is clearly intolerable. From ....

Jacobson, V.: Compressing TCP/IP Headers for Low-Speed Serial Links. Internet Request for Comments 1144, February 1990.

....ideas, fulfilling the meta goal that the work should have wide impact. 125 1 Internet Gateways, Intermediaries, and Composable Applications The ability to interpose intermediaries between a client and server has historically been used for various kinds of network and application adaptation [83, 62]. By formalizing the proxy interface and making it symmetric to the client server interface, the HTTP proxy mechanism [91] makes makes the proxy a first class Web entity, and directly enables not only passive caching but also filtering, anonymization [20] and value added services involving ....

....Client Adaptation By Proxy Interposition Various forms of proxy like interposition have been explored at both the network level and the application level. On the fly compression, especially for protocol metadata at the network level, has long been used to mitigate the effects of slow networks [83, 62]. Various network and transport level optimizations have also been used to address the wireless case [8] which has propagation and error characteristics quite different from those of most wired networks. As we discussed, a proxied model such as TACC enables dynamic adaptation mechanisms, which ....

Van Jacobson. Compressing TCP/IP headers for low-speed serial links. RFC 1144, February 1990. 158

....or UDP session, however this would require extensive modification of the BSD 4.3 IP code 2 . An alternative, which has not yet been implemented, would be to identify the higher layer TCP and UDP associations within the ATM driver in a similar manner to that used in SLIP header compression [11]. 6.1 IP Address Resolution To set up an ATM connection for tunnelling IP packets, the IP tunnelling code must somehow resolve the IP address to form an ATM address. It was a particular choice of our design that this mapping would be performed by the manager, and so we permit AF INET addresses to ....

V. Jacobson. Compressing TCP/IP Headers for Low-Speed Serial Links. RFC-1144, February 1990.

....datagram header encoding, compresses TCP IP headers through differential encoding. It takes advantage of the predictable changes between successive headers for the same TCP connection. This encoding scheme has been previously demonstrated to achieve a 10 to 1 compression ratio of TCP IP headers [48]. In our calculations, we assume the same compression ratio for 40 byte TCP IP headers but leave 28 byte UDP IP headers intact. Although the transmission efficiency advantages of these compression techniques are evident in Figures 5.7 through 5.9 and Tables 5.3 through 5.5, two concerns remain: ....

....header encoding is currently used in the Internet by hosts connected to low speed serial lines. Predictive differential encoding of TCP IP headers has been implemented with minor modifications to the Unix kernel operating system kernel. The nature of these modifications are documented in Reference [48]. They are also included in the Serial Line IP (SLIP) software distribution that has been used for several years throughout the Internet. The same techniques are applicable within an ATM network if each TCP connection maps to a separate virtual circuit in a connection oriented ATM network. ....

V. Jacobson, Compressing TCP/IP Headers for Low-Speed Serial Links, Network Working Group Request for Comments 1144, February, 1990.

....agent on this link) is required, even if using a co located care of address. B The foreign agent is busy. H The agent is a home agent. F The agent is a foreign agent. M Minimal encapsulation (RFC 2004 [20] G GRE encapsulation (RFC 1701 [11] V Van Jacobson header compression (RFC 1144 [13]) Note that bits F and H are not mutually exclusive, and that B cannot be set unless F is also set. Note also that a foreign agent typically needs to continue sending advertisements out (with the B bit set) even though it is too busy to provide service to new mobile nodes. Otherwise, ....

Van Jacobson. Compressing TCP/IP Headers for Low-Speed Serial Links. RFC 1144, February 1990.

....to the same destination [18] He called such a burst a packet train. He said that if the spacing between two packets exceeds some inter train gap, that these packets belong to separate trains. In subsequent years, several protocol stack implementations were optimized to exploit this phenomenon [4, 16]. More recently, other investigators found that due to the high degree of multiplexing, back to back packet trains are not as prominent on wide area networks as they are for local area networks [14, 10] Researchers are already calling for a definition of packet trains for wide area networks [21] ....

Van Jacobson. Compressing TCP/IP headers for low-speed serial links. Technical Report RFC1144, LBL, February 1990.

....were IBM ThinkPad 701C laptops (25 75MHz i80486DX4) running Linux 1.2.8. All of the machines were otherwise idle during the tests. The network options consisted of switched 10 Mbit s Ethernet, 2 Mbit s wireless AT T WaveLAN, and Serial Line IP with Van Jacobson TCP IP header compression (CSLIP) [20] over 19.2 Kbit s V.32turbo wired and 9.6 Kbit s ETC cellular dial up links 1 . To minimize the effects of network traffic on our experiments, the switched Ethernet was configured such that the server, the ThinkPad Ethernet adapter, and the WaveLAN base station were the only machines on the ....

V. Jacobson. Compressing TCP/IP Headers for Low-Speed Serial Links. Internet RFC 1144, February 1990.

....by only one cell header and at most one adaptation header and trailer. The third technique compresses TCP IP headers through differential encoding, taking advantage of the predictable changes between successive headers for the same TCP connection. Using such an encoding scheme, Jacobson [15] has demonstrated a 10 to 1 compression ratio of TCP IP headers over serial links. We assume the same compression ratio for 40 byte TCP IP headers but leave 28 byte UDP IP headers intact. 6.4. Summary of Results In addition to the results shown in Tables 4 and 5, we calculated efficiency for ....

V. Jacobson, Compressing TCP/IP Headers for Low-Speed Serial Links, Network Working Group Request for Comments 1144, February, 1990.

....related to the unreliable nature of wireless media are somewhat similar to the ones which surfaced in the early eighties when telephone and serial lines were used to connect personal computers to the Internet. Thinwire protocols[7] attempted to alleviate some of those problems. Header compression[11] for TCP connections was suggested for improving the response time of interactive applications such as telnet on low speed links. Although these solutions are applicable to some extent to wireless links, they do not deal with host mobility. In addition, such solutions cannot adapt to the changes ....

V. Jacobson. Compressing TCP/IP headers for low-speed serial links. Request for Comments 1144, February 1990.

....160 bits long, has about 127 bits of probable plaintext, and the TCP header has about 124 bits predictable out of 160. That there is considerable redundancy here is not surprising. Indeed, the same observation was made, albeit in a rather different context, in the design of PPP header compression [18]. When predictable header fields are added to the redundancy in the user s data, it becomes apparent that exhaustive search cryptanalysis is quite feasible even without known plaintext. 6. Traffic Analysis Probable plaintext attacks are not carried out on a whim. They require expensive, ....

....defender s advantage. A more promising approach might be to use a keyed compression function. For example, the compression dictionary could be modified based on the keying material. A different approach to compression might be to use semantic knowledge, along the lines of PPP header compression [18]. For example, it may be possible to send abbreviated sequence and acknowledgment fields. If perconnection keying is used, IP addresses and port numbers are implicit in the security association and need not be sent. The replay counter is more troublesome; more or less by definition, it can t be ....

V. Jacobson. Compressing TCP/IP headers for low-speed serial links. Request for Comments (Proposed Standard) RFC 1144, Internet Engineering Task Force, Feb. 1990.

....workstations are also used as clients of other workstations. The network options consist of switched 10 Mbit s Ethernet, 2 Mbit s wireless AT T WaveLAN, 128 Kbit s and 64 Kbit s Integrated Digital Services Network (ISDN) links, and Serial Line IP with Van Jacobson TCP IP header compression (CSLIP) [14] over 19.2 Kbit s V.32terbo wired and 9.6 Kbit s Enhanced Throughput Cellular (ETC) cellular dial up links. 5.2 Baseline Performance The test environment consisted of a single server and multiple clients. The server machine was a Intel Advanced EV workstation running the standalone TCP server. ....

V. Jacobson. Compressing TCP/IP Headers for Low-Speed Serial Links. Internet RFC 1144, February 1990.

....any sort of device driver could live below IPSEC, our current implementation assumes an Ethernet driver. An obvious extension would be PPP compatability, though encryption interacts poorly with modem based compression and the authentication header would interfere with TCP header compression [5]. 3.1 Output Processing When the IPSEC module receives a packet from above, it must look at the destination address, build an IPSEC header, perform the necessary security operations (authentication and or encryption) determine the IP address of the endpoint of the cryptographic association, and ....

V. Jacobson. Compressing TCP/IP headers for low-speed serial links. Request for Comments (Proposed Standard) RFC 1144, Internet Engineering Task Force, February 1990.

....version control represent intermediate versions as deltas; SCCS starts with an original version and encodes subsequent ones with forward deltas, whereas RCS encodes previous versions as reverse deltas from their successors. Jacobson s technique for compressing IP and TCP headers over slow links [10] uses a clever, highly specialized form of delta encoding. In spite of this history, it appears to have taken several years before anyone thought of applying delta encoding to HTTP, perhaps because the development of HTTP caching has been somewhat haphazard. The first published suggestion for ....

V. Jacobson. Compressing TCP/IP Headers for LowSpeed Serial Links. RFC 1144, February, 1990.

....as clients of other workstations. Network options that we have experimented with include 10 Mbit s switched Ethernet, 2 Mbit s wireless AT T WaveLAN, 128 Kbit s and 64 Kbit s Integrated Digital Services Network (ISDN) links, and Serial Line IP with Van Jacobson TCP IP header compression (CSLIP) [43] over 19.2 Kbit s V.32terbo wired and 9.6 Kbit s Enhanced Throughput Cellular (ETC) cellular dial up links 2 . The test environment consisted of a single server and multiple clients. The server machine was an Intel Advanced EV workstation running the standalone TCP IP server. The clients were ....

V. Jacobson, Compressing TCP/IP Headers for Low-Speed Serial Links, Internet RFC 1144, Feb. 1990.

....5. Performance Results The performance of the MDCP protocol was tested in four sets of experiments totaling in 50 hours of air time . Our experiments indicate that in a wireless environment the performance of our approach is superior to regular TCP IP on top of PPP with header compression [Jac90] enabled. Data Channel Service for Wireless Telephone Links 11 Table 1: Hardware Used in the Measurements Mobile Node DECpc 325 SL, 386SX 25 MHz, 8 Mbytes of main memory Mobile Connection Host AMBRA Sprinta 486, 486SX 25 MHz, 8 Mbytes of main memory LAN Fixed Host PMC, Pentium 90 MHz, 16 ....

V. Jacobson. Compressing TCP/IP Headers for Low-Speed Serial Links. Request for Comments 1144, Network Information Center, February 1990.

....Filter (BPF) 13] and a modified version of tcpdump [17] These two packages are used to gather compression statistics. Custom filters were developed to parse the tcpdump files. The compression mechanisms utilized by the testbed include the popular Van Jacobson TCP Header compression mechanism [9] and a compressor that is based on the LZW scheme used in the BSD compress program. The LZW scheme was modified to operate in a packet based environment. Specifically, the system works by packetizing an arbitrarily long input stream. It constantly monitors the packet sizes and always sends the ....

V. Jacobson. Compressing TCP/IP headers for Low-Speed Serial Links. RFC 1144, Network Working Group, Feb. 1990.

....payload over a low speed serial link. Although solutions have been presented that compress the RTP header, either on an end to end or a hop by hop basis, the most promising design entails hop by hop IP UDP RTP header compression and is a direct application of the TCP IP header compression scheme [CTCP90] as applied to a low speed point to point link [CRTP96] In those instances, the combined 40 byte header often can be reduced down to 2 4 bytes for most packets. 5.3 Scalable Reliable Multicast There has been ample research devoted to the creation of a generic reliable multicast protocol with the ....

.... 128 kbps video) but these streams use fairly low quality encoding schemes [MBone94a, MBone94b] Regardless of encoding scheme or data compression scheme, the Internet community is working toward compression techniques to reduce protocol header overhead, which improve bandwidth limitation problems [ISSLL96, IPv6compress96, CTCP90, CRTP96]. Figure 6 Applications for image, video and audio compression [Compress95] 7.2.1.2 Bandwidth Sharing Even if there were enough bandwidth to accommodate an HDTV application, the HFC network is meant to be shared among subscribers. In [Thruput96] a hypothetical but optimistic usage profile is ....

V. Jacobson. Compressing TCP/IP Headers for Low-speed Serial Links. RFC1144. Feb 1990. Available as ftp://ftp.isi.edu/in-notes/ rfc1144.{ps.txt}

....to be a TCP IP packet and also carry the useful TCP timestamp option, which allows for a more accurate estimate of a TCP connection s RTT. S.Y. Wang, H.T. Kung Use of TCP Decoupling in Improving TCP Performance over Wireless Networks 19 Using the TCP header compression algorithm proposed in [32] and the twice algorithm proposed in [23] on wireless links, one can greatly reduce the size of header packets (and thus their PERs) without the bad effects on TCP s performance caused by dropping a headercompressed packet [23] The TCP header compression mechanism can compress the TCP IP header ....

V. Jacobson, Compressing TCP/IP Headers for Low-Speed Serial Links, RFC 1144.

No context found.

V. Jacobson. IP headers for low-speed serial links. RFC 1144, Internet Engineering Task Force, February 1990.

No context found.

Jacobson, V. (1990c) Compressing TCP/IP Headers for Low-Speed Serial Links, IETF RFC 1144

No context found.

V. Jacobson. Compressing TCP/IP headers for lowspeed serial links. RFC 1144, February 1990.

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